sunet/doc/latex/code.sty

% code.sty: -*- latex -*-
% Latex macros for a "weak" verbatim mode.
% -- like verbatim, except \, {, and } have their usual meanings.

% Environments: code, tightcode,  codeaux, codebox, centercode
% Commands: \dcd, \cddollar, \cdmath, \cd, \codeallowbreaks, \codeskip, \^
% Already defined in LaTeX, but of some relevance: \#, \$, \%, \&, \_, \{, \}

% Changelog at the end of the file.

% These commands give you an environment, code, that is like verbatim
% except that you can still insert commands in the middle of the environment:
%     \begin{code}
%     for(x=1; x<loop_bound; x++)
%         y += x^3; /* {\em Add in {\tt x} cubed} */
%     \end{code}
%
% All characters are ordinary except \{}. To get \{} in your text, 
% you use the commands \\, \{, and \}.

% These macros mess with the definition of the special chars (e.g., ^_~%).
% The characters \{} are left alone, so you can still have embedded commands:
%	\begin{code} f(a,b,\ldots,y,z) \end{code}
% However, if your embedded commands use the formerly-special chars, as in
%    	\begin{code} x := x+1 /* \mbox{\em This is $y^3$} */ \end{code}
% then you lose. The $ and ^ chars are scanned in as non-specials,
% so they don't work. If the chars are scanned *outside* the code env,
% then you have no problem:
% 	\def\ycube{$y^3$}
% 	\begin{code} x := x+1 /* {\em This is \ycube} */ \end{code}
% If you must put special chars inside the code env, you do it by
% prefixing them with the special \dcd ("decode") command, that
% reverts the chars to back to special status:
%    	\begin{code} x := x+1 /* {\dcd\em This is $y^3$} */ \end{code}
% \dcd's scope is bounded by its enclosing braces. It is only defined within
% the code env. You can also turn on just $ with the \cddollar command;
% you can turn on just $^_ with the \cdmath command. See below.
%
% Alternatively, just use \(...\) for $...$, \sp for ^, and \sb for _.

% WARNING:
% Like \verb, you cannot put a \cd{...} inside an argument to a macro
% or a command. If you try, for example,
%     \mbox{\cd{$x^y$}}
% you will lose. That is because the text "\cd{$x^y$}" gets read in
% as \mbox's argument before the \cd executes. But the \cd has to
% have a chance to run before LaTeX ever reads the $x^y$ so it can
% turn off the specialness of $ and ^. So, \cd has to appear at
% top level, not inside an argument. Similarly, you can't have
% a \cd or a \code inside a macro (Although you could use \gdef to
% define a macro *inside* a \cd, which you could then use outside.
% Don't worry about this if you don't understand it.)

% BUG: In the codebox env, the effect of a \dcd, \cddollar, or \cdmath
%   command is reset at the end of each line. This can be hacked by
%   messing with the \halign's preamble, if you feel up to it.

% Useage note: the initial newline after the \begin{code} or 
%   \begin{codebox} is eaten, but the last newline is not.
%   So,
%     \begin{code}
%     foo
%     bar
%     \end{code}
%  leaves one more blank line after bar than does
%     \begin{code}
%     foo
%     bar\end{code}
%  Moral: get in the habit of terminating code envs without a newline
%  (as in the second example).
%

% All this stuff tweaks the meaning of space, tab, and newline.
%===============================================================================
% \cd@obeyspaces
% Turns all spaces into non-breakable spaces.
% Note: this is like \@vobeyspaces except without spurious space in defn.
% @xobeysp is basically a space; it's defined in latex.tex.
%
{\catcode`\ =\active\gdef\cd@obeyspaces{\catcode`\ =\active\let =\@xobeysp}}



% \cd@obeytabs
% Turns all tabs into 8 non-breakable spaces (which is bogus).
%
{\catcode`\^^I=\active %
  \gdef\cd@obeytabs{\catcode`\^^I=\active\let^^I=\cd@tab}}

\def\cd@tab{\@xobeysp\@xobeysp\@xobeysp\@xobeysp\@xobeysp\@xobeysp\@xobeysp\@xobeysp}



% \cd@obeylines
% Turns all cr's into linebreaks. Pagebreaks are not permitted between lines.
% This is copied from lplain.tex's \obeylines, with the cr def'n changed.
%
{\catcode`\^^M=\active % these lines must end with %
  \gdef\cd@obeylines{\catcode`\^^M=\active\let^^M=\cd@cr}}

% What ^M turns into. This def'n keeps blank lines from being compressed out.
\def\cd@cr{\par\penalty10000\leavevmode} 	% TeX magicness
%\def\cd@cr{\par\penalty10000\mbox{}}		% LaTeX


% \codeallowbreaks
% Same as \cd@obeylines, except pagebreaks are allowed.
% Put this command inside a code env to allow pagebreaks.

{\catcode`\^^M=\active % these lines must end with %
  \gdef\codeallowbreaks{\catcode`\^^M\active\let^^M\cd@crbr}}

%\def\cd@crbr{\leavevmode\endgraf} % What ^M turns into.
\def\cd@crbr{\par\leavevmode} % What ^M turns into.


% \cd@obeycrsp 
% Turns cr's into non-breakable spaces. Used by \cd.

{\catcode`\^^M=\active % these lines must end with %
  \gdef\cd@obeycrsp{\catcode`\^^M=\active\let^^M=\@xobeysp}}

% =============================================================================

% Set up code environment, in which most of the common special characters
% appearing in code are treated verbatim, namely: $&#^_~%
% \ { } are still enabled so that macros can be called in this
% environment.  Use \\, \{, and \} to use these characters verbatim
% in this environment.
% 
% Inside a group, you can make
% all the hacked chars	special with the	\dcd		command
% $			special with the 	\cddollar	command
% $^_			special with the	\cdmath		command.
% If you have a bunch of math $..$'s in your code env, then a global \cddollar
% or \cdmath at the beginning of the env can save a lot of trouble.
% When chars are special (e.g., after a \dcd), you can still get #$%&_{} with
% \#, \$, \%, \&, \_, \{, and \} -- this is standard LaTeX.
% Additionally, \\ gives \ inside the code env, and when \cdmath
% makes ^ special, it also defines \^ to give ^.

%The hacked characters can be made special again
% within a group by using the \dcd command.

% Note: this environment allows no breaking of lines whatsoever; not
% at spaces or hypens.  To arrange for a break use the standard \- command,
% or a \discretionary{}{}{} which breaks, but inserts nothing.  This is useful,
% for example for allowing hypenated identifiers to be broken, e.g.
% \def\={\discretionary{}{}{}} %optional break
% FOO-\=BAR.

\def\setupcode{\parsep=0pt\parindent=0pt%
  \normalfont\ttfamily\frenchspacing\catcode``=13\@noligs%
  \def\\{\char`\\}%
  \let\dcd=\cd@dcd\let\cddollar=\cd@dollarspecial\let\cdmath=\cd@mathspecial%
  \@makeother\$\@makeother\&\@makeother\#%
  \@makeother\^\@makeother\_\@makeother\~%
  \@makeother\%\cd@obeytabs\cd@obeyspaces}
% other: $&#^_~%
% left special: \{}
% unnecessary: @`'"


%% codebox, centercode
%%=============================================================================
%% The codebox env makes a box exactly as wide as it needs to be
%% (i.e., as wide as the longest line of code is). This is useful
%% if you want to center a chunk of code, or flush it right, or
%% something like that. The optional argument to the environment,
%% [t], [c], or [b], specifies how to vertically align the codebox,
%% just as with arrays or other boxes. Default is [c].

%% Must be a newline immediately after "\begin{codebox}[t]"!

{\catcode`\^^M=\active % these lines must end with %
  \gdef\cd@obeycr{\catcode`\^^M=\active\let^^M=\cr}}

% If there is a [<letter>] option, then the following newline will
% be read *after* ^M is bound to \cr, so we're cool. If there isn't
% an option given (i.e., default to [c]), then the @\ifnextchar will
% gobble up the newline as it gobbles whitespace. So we insert the
% \cr explicitly. Isn't TeX fun?
\def\codebox{\leavevmode\@ifnextchar[{\@codebox}{\@codebox[c]\cr}} %]

\def\@codebox[#1]%
  {\hbox\bgroup$\if #1t\vtop \else \if#1b\vbox \else \vcenter \fi\fi\bgroup%
   \tabskip\z@\setupcode\cd@obeycr% just before cd@obey
   \halign\bgroup##\hfil\span}

\def\endcodebox{\crcr\egroup\egroup\m@th$\egroup}

% Center the box on the page:
\newenvironment{centercode}%
  {\begin{center}\begin{codebox}[c]}%
  {\end{codebox}\end{center}}


%% code, codeaux, tightcode
%%=============================================================================
%% Code environment as described above. Lines are kept on one page.
%% This actually works by setting a huge penalty for breaking
%% between lines of code. Code is indented same as other displayed paras.
%% Note: to increase left margin, use \begin{codeaux}{\leftmargin=1in}.

% To allow pagebreaks, say \codeallowbreaks immediately inside the env.
% You can allow breaks at specific lines with a \pagebreak form.

%% N.B.: The \global\@ignoretrue command must be performed just inside
%% the *last* \end{...} before the following text. If not, you will
%% get an extra space on the following line. Blech.

%% This environment takes two arguments. 
%% The second, required argument is the \list parameters to override the
%%     \@listi... defaults.
%%     - Usefully set by clients: \topsep \leftmargin
%%     - Possible, but less useful: \partopsep
%% The first, optional argument is the extra \parskip glue that you get around
%%     \list environments. It defaults to the value of \parskip.
\def\codeaux{\@ifnextchar[{\@codeaux}{\@codeaux[\parskip]}} %]
\def\@codeaux[#1]#2{%
  \bgroup\parskip#1%
	 \begin{list}{}%
	       {\parsep\z@\rightskip\z@\listparindent\z@\itemindent\z@#2}%
	       \item[]\setupcode\cd@obeylines}%
\def\endcodeaux{\end{list}\leavevmode\egroup\ignorespaces\global\@ignoretrue}

%% Code env is codeaux with the default margin and spacing \list params:
\def\code{\codeaux{}} \let\endcode=\endcodeaux

%% Like code, but with no extra vertical space above and below.
\def\tightcode{\codeaux[=0pt]{\topsep\z@}}%
\let\endtightcode\endcodeaux
%  {\vspace{-1\parskip}\begin{codeaux}{\partopsep\z@\topsep\z@}}%
%  {\end{codeaux}\vspace{-1\parskip}}



% Reasonable separation between lines of code
\newcommand{\codeskip}{\penalty0\vspace{2ex}}


% \cd is used to build a code environment in the middle of text.
% Note: only difference from display code is that cr's are taken
% as unbreakable spaces instead of linebreaks.

\def\cd{\leavevmode\begingroup\ifmmode\let\startcode=\startmcode\else%
	\let\startcode\starttcode\fi%
	\setupcode\cd@obeycrsp\startcode}

\def\starttcode#1{#1\endgroup}
\def\startmcode#1{\hbox{#1}\endgroup}


% Restore $&#^_~% to their normal catcodes
% Define \^ to give the ^ char.
% \dcd points to this guy inside a code env.
\def\cd@dcd{\catcode`\$=3\catcode`\&=4\catcode`\#=6\catcode`\^=7%
	   \catcode`\_=8\catcode`\~=13\catcode`\%=14\def\^{\char`\^}}

% Selectively enable $, and $^_ as special.
% \cd@mathspecial also defines \^ give the ^ char.
% \cddollar and \cdmath point to these guys inside a code env.
\def\cd@dollarspecial{\catcode`\$=3}
\def\cd@mathspecial{\catcode`\$=3\catcode`\^=7\catcode`\_=8%
		    \def\^{\char`\^}}


% Change log:
% Started off as some macros found in C. Rich's library.
% Olin 1/90:
% Removed \makeatletter, \makeatother's -- they shouldn't be there,
%   because style option files are read with makeatletter. The terminal
%   makeatother screwed things up for the following style options.
% Olin 3/91:
% Rewritten. 
% - Changed things so blank lines don't get compressed out (the \leavevmove
%   in \cd@cr and \cd@crwb). 
% - Changed names to somewhat less horrible choices. 
% - Added lots of doc, so casual hackers can more easily mess with all this.
% - Removed `'"@ from the set of hacked chars, since they are already
%   non-special. 
% - Removed the bigcode env, which effect can be had with the \codeallowbreaks
%   command.
% - Removed the \@noligs command, since it's already defined in latex.tex.
% - Win big with the new \dcd, \cddollar, and \cdmath commands.
% - Now, *only* the chars \{} are special inside the code env. If you need
%   more, use the \dcd command inside a group.
% - \cd now works inside math mode. (But if you use it in a superscript,
%   it still comes out full size. You must explicitly put a \scriptsize\tt
%   inside the \cd: $x^{\cd{\scriptsize\tt...}}$. A \leavevmode was added
%   so that if you begin a paragraph with a \cd{...}, TeX realises you
%   are starting a paragraph.
% - Added the codebox env. Tricky bit involving the first line hacked
%   with help from David Long.
% Olin 8/94
% Changed the font commands for LaTeX2e.